Bicycle frame with passive seat tube pivot joint

ABSTRACT

A bicycle frame assembly that includes an upper frame member and a lower frame member that each extend between a head tube and a dropout. A seat tube extends between the upper frame member and the lower frame member. The seat tube is preferably connected to a bottom bracket of the lower frame member and is connected by a pivot to the upper frame member so that the seat tube can deflect from a rest position without altering an orientation of a top tube to a bottom tube of the upper and lower frame members, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/342,615, filed Jan. 3, 2012, titled “Bicycle Frame With Passive SeatTube Pivot Joint,” which claims priority to U.S. Provisional PatentApplication Ser. No. 61/430,011 filed on Jan. 5, 2011 both of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to bicycles and, more particularly, to abicycle frame assembly wherein the seat tube is connected at anoverlapping intersection of a top tube and the seat stays by a passivepivot that allows the seat stay to deflect from a generally linearat-rest orientation to improve the vertical compliance of the bicycleframe.

The primary structural component of a conventional two-wheel bicycle isthe frame. On a conventional road bicycle, the frame is typicallyconstructed from a set of tubular members assembled together to form theframe. For many bicycles, the frame is constructed from members commonlyreferred to as the top tube, down tube, seat tube, seat stays and chainstays, and those members are joined together at intersections commonlyreferred to as the head tube, seat post, bottom bracket and reardropout. The top tube usually extends from the head tube rearward to theseat tube. The head tube, sometimes referred to as the neck, is a shorttubular structural member at the upper forward portion of the bicyclewhich supports the handlebar and front steering fork, which has thefront wheel on it. The down tube usually extends downwardly and rearwardfrom the head tube to the bottom bracket, the bottom bracket usuallycomprising a cylindrical member for supporting the pedals and chaindrive mechanism which powers the bicycle. The seat tube usually extendsfrom the bottom bracket upwardly to where it is joined to the rear endof the top tube. The seat tube also usually functions to telescopicallyreceive a seat post for supporting a seat or saddle for the bicyclerider to sit on.

The chain stays normally extend rearward from the bottom bracket. Theseat stays normally extend downwardly and rearward from the top of theseat tube. The chain stays and seat stays are normally joined togetherwith a rear dropout for supporting the rear axle of the rear wheel. Theportion of the frame defined by the head tube, seat post and bottombracket and the structural members that join those three items togethercan be referred to as the main front triangular portion of the frame,with the seat stays and chain stays defining a rear triangular portionof the frame. The foregoing description represents the construction of aconventional bicycle frame which of course does not possess a suspensionhaving any shock absorbing characteristics.

Although the increased popularity in recent years of off-road cycling,particularly on mountains and cross-country, has made a shock absorbingsystem in many instances a biking necessity. An exemplary rear wheelsuspension system is disclosed in U.S. Pat. No. 7,837,213. Generally,bicycle suspension systems intended for off-road riding conditionsinclude a number of links that are connected and movable or pivotable toallow the bicycle frame to absorb a portion of the energy associatedwith aggressive riding over uneven terrain. However, such robustsuspension systems do not particularly lend themselves to extended ridesover paved terrain. The robust nature of such systems increases theweight attributable to the bicycle assembly. During rides intended totest rider stamina, endurance, and conditioning, such robust suspensionsystems would detrimentally affect rider time performance.

Fixed shape forward and rear triangle frame shapes are generally wellaccepted as the preferred configuration for many road bicycles due totheir collective light weight and robust frame. However, even pavedsurfaces can present discontinuities wherein most riders would prefersome degree of bicycle suspension to limit or reduce the forcescommunicated to the rider from payment discontinuities. The everincreasing capabilities of bicyclists have created a sub-set of the roadbicycle termed an endurance bicycle. Endurance bicycles are generallyunderstood as race-ready road bicycles with added comfort to allowriders to complete rides of ever increasing duration and/or distance.Many endurance bicycles maintain a fixed forward and rear triangle frameand provide impact dampening with suspension seat posts and/or vibrationdampening handlebar assemblies.

An alternate approach to an endurance bicycle is disclosed in U.S. Pat.No. 6,932,371. U.S. Pat. No. 6,932,371 discloses a bicycle assemblywherein the seat tube forms a passive suspension element via theelimination of the seat stays and providing a second set of chain staysthat are located in closer proximity to the bottom bracket that to thetop tube. The frame assembly of U.S. Pat. No. 6,932,371 includes anumber of gusset members that are required to provide the desirednon-vertical stiffness of the frame assembly. In achieving the desiredvertical compliance, the bicycle frame of U.S. Pat. No. 6,932,371includes a number of supplemental structures that, in improving verticalcompliance, detrimentally affect the overall weight of the underlyingbicycle assembly.

Accordingly, there is a desire to provide a bicycle frame assembly thatincludes a passive suspension element but does not appreciablydetrimentally affect the weight of the overall bicycle frame assembly.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a bicycle frame assembly having adeflectable seat tube that overcomes one or more of the aforementioneddrawbacks. One aspect of the invention discloses a bicycle frameassembly having an upper frame member and a lower frame member. Theupper frame member includes a top tube and a pair of seat stays andextends between a dropout and a head tube in a generally continuousmanner. The lower frame member includes a bottom tube, a bottom bracket,and a chain stay and extends between the dropout and the head tube. Aseat tube extends from the lower frame member toward the upper framemember and passes beyond the top tube. The seat tube is connected to theupper frame member by a pivot so that more of the seat tube is locatedbetween the pivot and the bottom bracket than extends beyond the upperframe member. Preferably, an opening is formed through the top tube or alug that connects the seat stays with the top tube. The seat tubepreferably passes through the opening in the upper frame member.Alternatively, the seat tube could be perforated or otherwise contouredto pass generally around the more horizontal structure of the top tubeand/or the seat stays. As another alternative, the seat tube could passrearward relative to the top tube so as to be positioned in the spacegenerally flanked by the seat stays.

Another aspect of the invention that is useable with one or more of theabove aspects discloses a bicycle frame assembly that includes a forwardframe triangle that includes a top tube and a bottom tube. The top tubeincludes a first end that is connected to a head tube and a second end.The bottom tube includes a first end that is connected to the head tubeand a second end. A bottom bracket is connected to the second end of thebottom tube. A seat tube extends in an upward direction from the bottombracket and a pair of seat stays is connected to the top tube andextends in a rearward direction beyond the forward frame triangle. Apivot connects the seat tube to the forward frame triangle proximate thetop tube at a location nearer a bicycle seat than the bottom bracket.The pivot allows that portion of the seat tube disposed between thepivot and the bottom bracket to deflect from an at rest position duringvertical loading of the seat tube.

Another aspect of the invention that is useable with one or more of theabove aspects discloses a bicycle frame assembly having an upper framemember that includes a top tube and a pair of seat stays. The upperframe member extends between a dropout associated with a rear wheel anda head tube. An opening is formed in the upper frame member. A lowerframe member that includes a bottom tube, a bottom bracket, and a chainstay extends between the dropout and the head tube. A seat tube extendsfrom the lower frame member toward the upper frame member and passesthrough the opening in the upper frame member. A pivot connects the seattube to the upper frame member proximate the opening so that more of theseat tube is located between the pivot and the bottom bracket thanextends beyond the upper frame member.

Another aspect of the invention that is useable with one or more of theabove aspects discloses a method of allowing deflection of a seat tube.A seat tube is connected to a bottom bracket. The seat tube is connectedto an upper frame member with a pivot that is located at an overlappingintersection of the seat tube and the upper frame member so that theseat tube can deflect from alignment along a line between the bottombracket and the pivot.

These and various other features and advantages of the present inventionwill be made apparent from the following detailed description and thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate one preferred embodiment presently contemplatedfor carrying out the invention.

FIG. 1 is a side elevation view of a bicycle having a bicycle frameassembly according to the present invention;

FIG. 2 is an elevated right hand perspective view of bicycle frameassembly shown in FIG. 1 with the wheels, seat, drive and handlebarassemblies removed therefrom;

FIG. 3 is a view similar to FIG. 2 of an intersection of the seat tubewith the upper frame member of the bicycle frame assembly shown in FIG.1;

FIG. 4 is a cross-section of the intersection of the seat tube with theupper frame member taken along line 4-4 shown in FIG. 3;

FIG. 5 is an exploded view of the assembly associated with theintersection of the seat tube and the upper frame member shown in FIG.3; and

FIG. 6 is a side elevation view of the bicycle frame assembly shown inFIG. 2 and shows the loaded and loaded configurations of the seat tubeassociated with use of the bicycle frame assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a bicycle 10 having a frame assembly 12 according to thepresent invention. Bicycle 10 includes a seat 16 and handlebars 18 thatare attached to frame assembly 12. A seat post 20 is connected to seat16 and slidably engages a seat tube 22 of frame assembly 12. A top tube24 and a down tube 26 extend forwardly from seat tube 22 to a head tube28 of frame 12. Handlebars 18 are connected to a stem or steer tube 30that passes through head tube 28 and is connected or integrally formedwith a fork crown 32. Understandably, handlebar 18 may include a stemthat is constructed to slidably engage an interior cavity of steer tube30. It is appreciated that one or more of the structures of bicycle 10and frame assembly 12 can be constructed from similar materials, avariety of different materials, and various combinations thereof.Preferably, frame assembly 12 and seat tube 22 are formed of metal-typematerials, such as aluminum-type materials, carbon fiber materials,and/or materials that are sufficiently formable and robust enough tosupport the rider of bicycle 10.

Fork assembly 14 includes a pair of fork blades or fork legs 34 thatextend from generally opposite ends of fork crown 32 and are constructedto support a front wheel assembly 36 at an end thereof or dropout 38.Dropouts 38 engage generally opposite sides of an axle 40 constructed toengage a hub 42 of front wheel assembly 36. A number of spokes 44 extendfrom hub 42 to a rim 46 of front wheel assembly 36. A tire 48 is engagedwith rim 46 such that rotation of hub 42 and rim 46, relative to forklegs 34, rotates tire 48.

Bicycle 10 includes a front brake assembly 50 having an actuator 52attached to handlebars 18 and a pair of brake pads 53 positioned ongenerally opposite sides of front wheel assembly 36. Brake pads 53 areconstructed to engage a brake wall 54 of rim 46 thereby providing astopping or slowing force to front wheel assembly 36. A rear wheelassembly 56 includes a brake assembly 58 similar to front wheel brakeassembly 50 but it is appreciated that one or both of front and rearwheel brake assemblies 50, 58 could be provided in other brakeconfigurations such as a disk brake assembly wherein a rotor and acaliper are positioned proximate one or more of front wheel axle 40 or arear axle 64, respectively. A rear wheel 66 is positioned generallyconcentrically about rear axle 64.

A pair of seat stays 62, 68 (FIG. 2) and a pair of chain stays 70, 71(FIG. 2) extend rearward relative to seat tube 22 and offset rear axle64 from a crankset 72. Crankset 72 includes a set of pedals 74 that isoperationally connected to a flexible drive member such as a chain 76via one or more variable diameter chain gears or a chain ring orsprocket 78. Rotation of chain 76 communicates a drive force to a gearcluster 80 positioned proximate rear axle 64. Gear cluster 80 isgenerally concentrically orientated with respect to rear axle 64 andincludes a number of variable diameter gears.

Gear cluster 80 is operationally connected to a hub 82 of rear wheel 66.A number of spokes 84 extend radially between hub 82 and a rim 86 ofrear wheel 66 of rear wheel assembly 56. As is commonly understood,rider operation of pedals 74 drives chain 76 thereby driving rear wheel66 which in turn propels bicycle 10. Fork assembly 14 is constructed tosupport a forward end 88 of bicycle 10 above a ground surface 90.Handlebar 18 is connected to frame 12 and fork assembly 14 such thatoperator manipulation of handlebar 18 is communicated to fork assembly14 to facilitate rotation of front wheel assembly 36 relative to frameassembly 12 along a longitudinal axis, indicated by arrow 175, ofbicycle 10. As is commonly understood, such manipulation of handlebar 18steers bicycle 10 during riding.

Understandably, the construction of bicycle 10 shown in FIG. 1 is merelyexemplary of a number of bicycle configurations. That is, whereasbicycle 10 is shown as what is commonly understood as a street or roadbike, it is appreciated that the present invention is applicable to anumber of bicycle configurations including those bicycles with moreaggression suspension systems commonly found in off-road or mountainbike frame configurations, and/or hybrids, cross-over or multi-purposebicycle frame configurations.

Referring to FIGS. 1 and 2, top tube 24 and seat stays 68 extend in afairly continuous manner to form an upper frame member 100 that extendsfrom head tube 28 to a pair of dropouts 102, 103 that support rear axle64. Upper frame member 100 can be formed as one piece and/or assembledfrom a distinct top tube 24, seat stays 68, and/or an optional lug 104that is disposed between the top tube 24 and the seat stays 68. It isappreciated that seat stays 62, 68 and top tube 24 of upper frame member100 could be formed as a unitary structure, a number of discretepermanently connected elements, or connected to one another via anoptional lug 104 associated with an overlap area 105 of seat tube 22 andupper frame member 100. In a similar manner, it is also appreciated thatdown tube 26, bottom bracket 110, and chain stays 70, 71, whoseassemblies collectively define a lower frame member that extends fromhead tube 28 to one or more dropouts 102, 103 could be formed as aunitary assembly wherein bottom bracket 110 is formed with down tube 26or chain stays 70, 71, or an assembly wherein the chain stays 70, 71 anddown tube 26 can be permanently affixed to a discrete bottom bracket lugor simply bottom bracket 110. Once assembled, as plainly shown in FIG.1, bicycle 10 includes a forward frame triangle that is a generallydefined by the triangular shape of the direction of extension of theseat tube, the top tube, and the down tube of frame assembly 12regardless of the methodology or number of discrete elements used toform the frame assembly.

As shown in FIG. 2, seat tube 22 includes a first end 108 that issecured to bottom bracket 110 of bicycle frame 12 and a second end 112that extends in a generally upward direction beyond the location of thelug or overlap area 105 with upper frame member 100. Preferably, seatpost 20 (FIG. 1) telescopically cooperates with seat tube 22 of frameassembly 12. A passive pivot assembly 120 connects an upper portion ofseat tube 22 to bicycle frame assembly 12 proximate overlap area 105such that more of seat tube 22 extends between pivot assembly 120 andbottom bracket 110 than extends in an upward direction relative to theintersection of seat tube 22 and upper frame member 100.

Passive pivot assembly 120 completes the linkage between upper framemember 100, which includes top tube 24 and the structures associatedwith seat stays 62, 68. A lower end of seat tube 22 is secured to lowerframe member 101, which includes the down tube 26 and bottom bracket 110and preferably one of more chain stays 70, 71. As explained above, seattube 22, top tube 24 and down tube 25 collectively generally define theforward triangle of frame assembly 12. Frame assembly 12 has a fairlyrobust and stable feel during use but is also constructed to provideimpact dampening performance in a manner that does not allow changing ofthe relative connection points of any of the respective members of theforward frame triangle. As described further below with respect to FIG.6, the non-bonded rigid yet pivotable connection of seat tube 22 withupper frame member 100 allows deflection of seat tube 22 in a verticalplane and in a direction along the longitudinal length of the seat tube22 so as to allow the frame assembly 12 to provide a limited degree ofsuspension performance or vertical compliance without altering theorientation of the connection points of any of the frame membersrelative to one another.

As shown in FIGS. 3-5, overlap area 105 includes a passage 130 that isshaped to allow seat tube 22 to pass therethrough. An opening 132 (FIG.5) is formed laterally through seat tube 22 and shaped to rotationallycooperate with pivot assembly 120. As mentioned above, it is envisionedthat seat tube 22 merely pass over an axis or longitudinal areaassociated with one or more of the top tube, the seat stays, and/or afabrication lug being formed therebetween. It is envisioned that theseat tube could be perforated or otherwise contoured to pass generallyaround the more horizontal structure of the top tube and/or the seatstays associated with upper frame member 100. As another alternative,the seat tube could pass rearward relative to the closed structure oftop tube 24 so as to be positioned in the space generally flanked by theseat stays. Each configuration allows limited passive pivoting betweenseat stays 70, 71 and the adjacent structure of upper frame member 100of bicycle frame assembly 12.

As shown in FIG. 3, passage 130 is bounded on a forward side 131 by anend wall associated with top tube 24 or a portion of the respectiveframe lug 104. A first optional gasket 134 is disposed between forwardside 131 of overlap area 105 and top tube 24 and generally surrounds aforward side 136, and opposite lateral sides 138, 140 of seat tube 22.Optional gasket 134 prevents moisture and/or dirt and/or debris fromentering the pivot area associated with passage 130 and the passage ofseat tube 22 therethrough but does not otherwise interfere with theflexion of seat tube 22 during use of bicycle 10 as described furtherbelow with respect to FIG. 6. Passage 130 is bounded on opposite lateralsides by side walls 142, 144 of upper frame member 100. An optional rearweb wall 146 completes the definition of passage 130 such that upperframe member 100 completely surrounds seat tube 22 with web wall 146extending laterally between seat stays 62, 68.

As shown in FIGS. 4 and 5, pivot assembly 120 includes a first bolt orother fastener 150, a second bolt or other fastener 152, a guide sleeve154, and first and second bearings or bushings 156, 158. Each offasteners 150, 152 includes a threaded portion 160, a stem portion 162,and a head portion 164. The radial diameter of each fastener 150, 152gradually increase from the respective threaded portion 160 to the stemportion 162 to the head portion 164. One or each of head portions 164includes a drive surface 166 that is shaped to cooperate with a drivingtool, such as a hex driver or the like for securing each of first andsecond fasteners 150, 152 relative to pivot assembly 120. Although shownas being formed on an interior radial surface of fasteners 150, 152, itis appreciated that driving surface 166 could have any number of shapesand/or be provided on a radial exterior surface of the correspondingfastener 150, 152. It is further appreciated that one of fasteners 150,152 could formed integrally with sleeve 154 such that operation of onerespective fastener secures pivot assembly 120 relative to bicycle frameassembly 12.

Each bushing 156, 158 includes an outer radial surface 170, an innerradial surface 172, an outboard lateral surface 174, and an inboardlateral surface 176. As used herein, the inboard and outboard lateraldirections associated with surfaces 174, 176 of each bushing 156, 158refers to the orientation of surfaces 170, 174 relative to alongitudinal vertical plane that contains longitudinal axis 175 ofbicycle 10 and the relative position of the respective surfaces and/orstructures relative to the same. For example, surfaces 176 of bushings156, 158 are nearer a longitudinal axis, indicated by line 178, of upperframe member 100. Accordingly, surfaces 174 are further outboard andsurfaces 176 are further inboard relative to one another andlongitudinal axis 178 of upper frame member 100 along a longitudinalaxis, indicated by line 180, of pivot assembly 120. As shown in FIG. 5,the longitudinal axis 180 of pivot assembly 120 is oriented in acrossing direction relative to, and is preferably normal to,longitudinal axis 178 of upper frame member 100.

Still referring to FIGS. 4 and 5, a first opening 184 and the secondopening 186 are formed in each of the respective sidewalls 142, 144 ofupper frame member 100 and centered along axis 180 of pivot assembly120. A seat 188 extends circumferentially about at least one of openings184, 186 in the lateral outboard facing surface of the respectivesidewall 142, 144. Seat 188 is defined by a lip 190 that extendscircumferentially about the corresponding opening 184, 186 and is shapedto cooperate with sleeve 154 and a corresponding bushing 156, 158.

Sleeve 154 includes a stem portion 194, the head portion 196, and anopening 198 formed therethrough. Sleeve 154 is constructed to slidablycooperate with openings 184, 186 in a direction aligned with axis 180.When assembled, head portion 196 of sleeve 154 traverses an overlappingarea between opening 184 and a seat 199 associated with opening 132 ofseat tube 22 as well as opening 200 associated with optional gasket 134.Optional gasket 134 includes a second opening 202 that, when assembled,is also concentrically oriented with respect axis 180 of pivot assembly120 and cooperates with the other of fasteners 150, 152. Opening 132 ofseat tube 22 circumferentially cooperates with stem portion 194 ofsleeve 154 when the longitudinal axis of opening 132 is aligned axis 180of pivot assembly 120. As explained further below with respect to FIG.6, the axis of opening 132 of seat tube 22 is formed along a plane,indicated by line 204, that is offset in a forward direction relative tolongitudinal axis 175 of bicycle 10 and with respect to a longitudinalaxis 206 of seat tube 22.

Threaded portions 160 of each fastener 150, 152 operatively cooperatewith a threaded surface 210 (FIG. 4) formed on an inner radial surfaceof sleeve 154. Bushings 156, 158 rotatably cooperate with stem portion162 of each of fasteners 150, 152 and cooperate with seats 188 definedby upper frame member 100. As shown in FIGS. 4 and 5, pivot assembly 120can include another optional gasket 214 that cooperates with thelaterally outboard directed sides of pivot assembly 120. Gasket 214includes a first arm 216 and a second arm 218 that extend in a generallyupward direction relative to a web wall 220. The laterally inboardfacing side of each arm 216, 218 includes a lip 221 that is shaped tosnuggly cooperate with a radially outboard directed surface of headportion 164 of a respective fastener 150, 152. Preferably, upper framemember 100 includes a recess 222 that is shaped to mimic the shape ofgasket 214 such that when assembled, gasket 214 provides a generallysmooth contour along the exterior surface of upper frame member 100associated with pivot assembly 120.

When assembled, pivot assembly 120 provides a secure connection betweenupper frame member 100 and seat tube 22 and does so in a manner thatprevents lateral, longitudinal, and vertical movement of seat tube 22relative to upper frame member 100 but allows rotation of seat tube 22about axis 180 associated with opening 132 which is collinear with pivotassembly 120 relative to upper frame member 100. Such a connectionallows only flexion or flexing movement of seat tube 22 relative to theother structural members of bicycle frame assembly 12 during use ofbicycle 10.

As mentioned above, other interactions between seat tube 22 and frameassembly 12 are envisioned that allow similar deflection of the seattube 22. For instance, seat tube 22 could include a passage like passage130 or otherwise be contoured so that the seat tube passed around thetop tube/seat stays/lug and/or such that the top tube/seat stays/lugpass through the seat tube. Still another alternative includesconnecting the seat stays to the upper frame member or top tube at alocation forward of the seat tube such that the seat tube would bepositioned in an area generally flanked by the seat stays. Referring toFIG. 6, although an axis, indicated by line 180, of pivot assembly 120is offset in an forward direction relative to the longitudinal axis 206of seat tube 22, is appreciated that axis 180 could be oriented tointersect axis 206 or offset in a rearward direction relative thereto soas to alter the deflection performance of seat tube 22 and/or to bettersuit the preferences of a given rider or class of users.

Referring to FIG. 6, during normal use of frame assembly 12, seat tube22 maintains a generally “at rest” configuration as represented by seattube 22 shown in FIG. 6. Preferably, seat tube 22 has a fairly linear atrest orientation. Understandably, during normal use, some initialdeflection of seat tube 22 may occur depending on the weight andpreferred orientation of the rider during normal use over relativelysmooth terrain. During an impact event, indicated by arrow 230, adownward and rearward bending moment is imparted to seat tube 22 by theinteraction of the rider with the rear portion of a saddle, which iscommonly offset to the rear of the longitudinal centerline 206 of seattube 22. Such loading of the seat tube allows seat tube 22 to pivot in apassive manner about pivot assembly 120 and results in a rearwarddeflection of an upper portion 232 of seat tube 22 positioned abovepivot assembly 120 and a forward deflection of a lower portion 234 ofseat tube 22 that is positioned between pivot assembly 120 and bottombracket 110 relative to the at-rest orientation.

The deflection of seat tube 22 relative to upper frame member 100 andlower frame member 101 is shown graphically in FIG. 6 by line 236. Sucha configuration allows near the entirety of seat tube 22 to deflect froman at rest position to a “bent” orientation, represented by line 236 toimprove the vertical compliance of frame assembly 12. Supporting anupper end of seat tube 22 proximate the intersection of seat tube 22with upper frame member 100 provides a fairly rigid feel of frameassembly 12 during all riding conditions but mitigates the communicationof undampened travel surface discontinuities to the rider via riderinteraction with the bicycle seat. Such performance improves ridercomfort and decreases rider discomfort commonly associated with extendedrides. Preferably, seat tube 22 deflects no more than 15 degrees from anat rest orientation and more preferably, seat tube 22 deflects no morethan 7 degrees from a rest position in response to rider interactionwith seat 16. Such a configuration has been shown to provide a desireddegree of responsiveness to rider interaction with the bicycle frame anddoes so in a manner that improves the vertical compliance of the bicycleframe assembly without unduly detracting from the same. However, it isappreciated that any desired range of deflection can be provided.Preferably, the greatest deflection value is associated with adeflection that a rider will tolerate and still feel comfortable on thebicycle during most riding conditions to a near unperceivable deflectionduring most riding conditions.

As shown in the experimental data below, frame assembly 12 providesgreater longitudinal deflection of the seat tube with comparable lateralstiffness for bicycle frames having similar shapes and with nearlynegligible contribution to the overall weight of the bicycle frameassembly. It is further envisioned that the forward and/or rearwardorientation of the pivot axis relative to the longitudinal axis of theseat tube can be manipulated to satisfy a wide variety of riderperformance preferences and/or to alter the deflection performance ofthe seat tube. It is further appreciated that the construction of theseat tube can be manipulated to further alter the vertical compliance ofthe frame assembly while providing a robust bicycle frame assembly.

Frame Weight Full Frame Torsional Head Tube Stiffness BB horizontaldeflection (2) Description Size Sample # (gram) Stiffness (inches) N * mper degree inches Vertical Compliance (inches) 6SRS 56 H3 2011-5428 8500.1885 78 56 0.86 Baseline 6SRS 56 H3 2011-5697 898 0.186  79* 54 1.38Pivot

As shown in the data provided above, configuring a bicycle frame withthe passive pivot connection between the seat tube and the upper framemember provides improved vertical compliance of the seat tube ofapproximately 60% with an increase in frame assembly weight ofapproximately 48 grams or only approximate 5% of the overall weight ofthe frame assembly. Accordingly, bicycle frame assembly 12 provides abicycle frame have acceptable frame responsiveness with improvedvertical compliance for improving rider comfort.

Therefore, one embodiment of the invention includes a bicycle frameassembly having a forward frame triangle that includes a top tube and abottom tube. The top tube includes a first end that is connected to ahead tube and a second end. The bottom tube includes a first end that isconnected to the head tube and a second end. A bottom bracket isconnected to the second end of the bottom tube. A seat tube extends inan upward direction from the bottom bracket. A pair of seat stays areconnected to the top tube and extend in a rearward direction beyond theforward frame triangle. A pivot connects the seat tube to the forwardframe triangle proximate the top tube at a location nearer a bicycleseat than the bottom bracket.

Another embodiment of the invention that includes one or more featurescombinable with the above embodiment includes a bicycle frame assemblyhaving an upper frame member that includes a top tube and a pair of seatstays. The upper frame member extends between a dropout associated witha rear wheel and a head tube. An opening is formed in the upper framemember. A lower frame member that includes a bottom tube, a bottombracket, and a chain stay extends between the dropout and the head tube.A seat tube extends from the lower frame member toward the upper framemember and passes through the opening in the upper frame member. A pivotconnects the seat tube to the upper frame member proximate the openingso that more of the seat tube is located between the pivot and thebottom bracket than extends beyond the upper frame member.

Another embodiment of the invention that is useable with one or more ofthe aspects of the above embodiments discloses a method of allowingdeflection of a seat tube. A seat tube is connected to a bottom bracket.The seat tube is connected to an upper frame member with a pivot that islocated at an overlapping intersection of the seat tube and the upperframe member so that the seat tube can deflect from alignment along aline between the bottom bracket and the pivot.

The present invention has been described in terms of the preferredembodiment, and it is recognized that equivalents, alternatives, andmodifications, aside from those expressly stated, are possible andwithin the scope of the appending claims.

What is claimed is:
 1. A bicycle frame assembly comprising: a forwardframe triangle comprising: a top tube having a first end connected to ahead tube and a second end; a bottom tube having a first end connectedto the head tube and a second end; a bottom bracket connected to thesecond end of the bottom tube; and a flexible, unitary seat tubeextending in an upward direction from the bottom bracket; a pair of seatstays connected to the top tube and extending in a rearward directionbeyond the forward frame triangle; and a pivot connecting the seat tubeto the forward frame triangle proximate the top tube at a locationnearer a bicycle seat than the bottom bracket.
 2. The bicycle frameassembly of claim 1, further comprising a passage formed proximate anintersection of the seat stays and the top tube and shaped toaccommodate the seat tube passing therethrough.
 3. The bicycle frameassembly of claim 2, wherein an axis of the pivot is oriented normal toan axis of the passage.
 4. The bicycle frame assembly of claim 1,wherein the flexible, unitary seat tube is made of a fiber reinforcedplastic.
 5. The bicycle frame assembly of claim 1, wherein the seat tubecan rotate at least 7 degrees about the pivot allowing the seat tube todeflect from an at rest shape.
 6. The bicycle frame assembly of claim 1,wherein a longitudinal axis of the pivot is one of positioned forward ofa longitudinal axis of the seat tube, aligned with the longitudinal axisof the seat tube, or positioned rearward the longitudinal axis of theseat tube.
 7. A bicycle frame assembly comprising: an upper frame memberthat includes a top tube and a pair of seat stays and that extendsbetween a dropout and a head tube; an opening formed in the upper framemember; a lower frame member that includes a bottom tube, a bottombracket, and a chain stay, and that extends between the dropout and thehead tube; a flexible, unitary seat tube extending from the lower framemember toward the upper frame member and passing through the opening inthe upper frame member; and a pivot connecting the seat tube to theupper frame member proximate the opening so that more of the seat tubeis located between the pivot and the bottom bracket than extends beyondthe upper frame member.
 8. The bicycle frame assembly of claim 7,wherein the pivot is oriented either forward or rearward relative to alongitudinal center-line of seat tube.
 9. The bicycle frame assembly ofclaim 7, further comprising a bridge that extends between the pair ofseat stays and defines a rear wall of the opening.
 10. The bicycle frameassembly of claim 7, wherein the flexible, unitary seat tube is made ofa fiber reinforced plastic.
 11. The bicycle frame assembly of claim 7,wherein the pivot includes a first portion and a second portion thatthreadably cooperate with one another.
 12. The bicycle frame assembly ofclaim 11, wherein each of the first portion and the second portion ofthe pivot include a head portion and a shank portion wherein only theshank portion passes through the upper frame member.
 13. A method ofallowing deflection of a seat tube, comprising: connecting a flexible,unitary seat tube to a bottom bracket; and connecting the seat tube toan upper frame member with a pivot located at an overlappingintersection of a seat tube and the upper frame member so that the seattube can deflect from alignment along an line between the bottom bracketand the pivot.
 14. The method of claim 13, further comprising definingan opening through the upper frame member that is shaped to allow theseat tube to pass therethrough.
 15. The method of claim 14, furthercomprising closing a forward facing, a rearward facing, and oppositelateral facing sides of the opening.
 16. The method of claim 13, furthercomprising forming the upper frame member with a pair of seat stays anda top tube.
 17. The method of claim 16, further comprising connectingthe pair of seat stays to one another at a location rearward of the seattube that is offset from a rear wheel.
 18. The method of claim 13,wherein the flexible, unitary seat tube is made of a fiber reinforcedplastic.
 19. The method of claim 13, further comprising providing agasket that cooperates with at least one longitudinal end of the pivot.20. The method of claim 13, further comprising forming the pivot as afirst part and a second part that removably cooperate with the seat tubeand engage the upper frame member from opposite lateral directionsrelative to a longitudinal direction of the upper frame member.